This is a solution I like for a portable generator. It is 3 position disconnect/safety switch, it allows you to plug in a generator safely and energize your entire home, not just a small number of circuits.
NOW you CAN NOT run everything at once but you can select what you need when you need it.
Step 1. plug Generator into home and start( Portables can have Elect. Start;))
step 2. Throw the Switch to generator and that's it!*** be sure to turn off non essential loads***
These typs of switches start @ $350 plus the install....I first seen this on a farm and the farmer had a Gen. unit that hooked up to his 3-point hitch/PTO on his tractor....OLD School!
NOT just a Generator! Inverter/battery could go here also